There are known prior art engine designs featuring a two-stroke internal combustion engine, including those described in U.S. Pat. Nos. 3,283,752 and 4,385,597 to Stelzer, No. 4,831,972 to Barnwell, No. 5,036,667 to Thatcher, and No. 5,285,752 to Reed et al. The Reed patent features rotary valves for fresh air intake, and this requires conversion of the linear piston motion to rotary motion, introducing additional friction. The Thatcher patent returns a portion of the power developed to force return of the combustion piston motion, decreasing output.
The Barnwell patent and the Stelzer patents feature extremely long piston rods, a portion of which are exposed beyond the cylinder, making them vulnerable to more-than-usual wear due to friction on entering and exiting the reaction chamber at each stroke. Leaking of fuel across the entry/exit barrier can occur as well as pressure gradients causing "bubbles" which can "choke" the engine at worst, or reduce Its efficiency at best. Thus, the exposed extra-long piston rods of the previous designs act as weak points, reducing the overall strength of the engine.
In the Steizer design, the single operating cycle does not allow for full exhaust of combustion gases, and there is a mixture of burnt gas and the fresh fuel supply, which reduces efficiency. As mentioned above, a portion of the piston is exposed beyond the cylinder, and the O-ring used to seal the piston exits and returns into the cylinder with each cycle, causing a shock against the O-ring on each re-insertion.
An additional weakness of the previous designs is the connection between the piston rod and the crankshaft. The above designs do not permit direct connection with the conventional type of crankshaft, so this involves additional loss of efficiency for the engine.
The prior art two-stroke internal combustion engine designs, therefore, suffered from intrinsic flaws detrimental to their sturdiness and efficiency, and represented radical departures from the standard practice. This made their adaptation to the existing market difficult.
In addition, the prior art designs do not allow for operation as a Diesel engine, requiring high compression ratios.
Therefore, it would be desirable to overcome the disadvantages associated with the prior art designs, and provide a sturdy, lightweight internal combustion engine providing increased efficiency.